1. Field of the Invention
The present invention relates to a system to mount a wheel to a brake drum. More specifically, the present invention relates to a system to mount a wheel to a brake drum with reduced heat transfer for extending tire life.
2. Description of the Prior Art
In an effort to reduce the unsprung weight of the tire/wheel/brake system on heavy duty over-the-road trucks to increase payload and improve performance, the wheel material has been changed from steel to aluminum while the brake drum has been redesigned for lighter weight using a centrifuge process to deposit a cast iron coating on a steel drum rather than a full cast iron drum. Both of these changes have dramatically reduced the overall weight of the wheel/brake combination thereby allowing for the carrying of additional cargo. However, the negative effect is that significantly more heat is conducted from the brake drum into the wheel and finally into the tire, specifically at the tire bead, which causes the tire service life to be reduced due to the elevated temperatures experienced during high duty cycle braking.
Various fins and air scoops have been fitted to the brake drum to improve heat dissipation into the surrounding air with some success. Also, airflow channels have been formed in the outer peripheral surface of the drum to promote airflow between the drum and the wheel to lower the tire operating temperature. U.S. Pat. Nos. 5,320,201; 2,059,170; 2,998,870 and British Patent No. 714,997, the disclosures of which are hereby expressly incorporated by reference describe such systems.
In spite of these efforts, the switch to centrifuge drums (where a cast iron braking surface is applied to a spinning steel drum) and aluminum wheels have resulted in a need for additional heat management to prevent overtemperature of the tire, especially at the tire bead.